Device in particular for drawing sheet-metal

ABSTRACT

A device, in particular for drawing sheet metal, having a drawing die which is movable in a cylinder by means of a piston and which can be moved towards the workpiece by the action of a pressure medium on a face of the piston, in which the face of the piston which is influenced by the pressure medium in the supply direction comprises a pressure rod which is connected to the piston and on which a further piston having a shell which encloses the pressure rod in a sealing manner is axially movable, in which the shell guides the pressure rod at a distance above the piston in a sleeve which has a smaller diameter than the cylinder and is closed at its end, the space in said sleeve being filled with a hydraulic liquid, the end of the shell having a smaller diameter exerting a hydraulically intensified pressure on the upper end of the pressure rod.

United States Patent 1191 Martin DEVICE IN PARTICULAR FOR DRAWING SHEET-METAL [76] Inventor: Johann Martin, Freiherr vom Steinstrasse 9, 6331 Oberbiel, Germany 22 Filed: Nov. 20, 1972 21 Appl. No.: 307,999 a [30] Foreign Application Priority Data Dec. 29, 1971 Germany 2165252 521 U.S. c1. 72/453, 60/560 51 1m. 01 B2lj 9/12 [58] Field of Search 72/453; 83/639; 60/547,. 60/560, 565, 583, 593; 74/583 [56] References Cited UNITED STATES PATENTS 1,940,304 12/1933 Jackson 60/560 FOREIGN PATENTS OR APPLICATIONS 845,150 8/l960 Great Britain 72/453 1451 May 7, 1974.

877,105 /1961 Great Britain 72/453 Primary ExaminerRichard J. Herbst Attorney, Agent, or Firm-Frank R. Trifari 57 ABSTRACT A device, in particular for drawing sheet metal, having a drawing die which is movable in a cylinder by means of a piston and which can be moved towards the workpiece by the action of a pressure medium on a face of the piston, in which the face of the piston which is influenced by the pressure medium in the supply direction comprises a pressure rod which is connected to the piston and on which a further piston having a shell which encloses the pressure rod in a sealing manner is axially movable, in which the shell guides the pressure rod at a distance above the piston in a sleeve which has a smaller diameter than the cylinder and is closed at its end, the space in said sleeve being filled with a hydraulic liquid, the endof the shell having a smaller diameter exerting a hydraulically intensified pressure on the upper end of the pressure rod.

6 Claims, 1 Drawing Figure fir DEVICE IN PARTICULAR FOR DRAWING SHEET-METAL The invention relates to a device, in particular for A is movable towards the workpiece by the action of a pressure medium on a face of the piston.

For a rational drawing of sheet metal it is necessary that the drawing dies can on the one hand be rapidly moved towards the workpiece and on the other hand that the various drawing devices with pressure dies can be placed closely beside each other. It is known to perform a coarse movement ata smaller pressure for the rapid movement of drawing dies towards the workpiece, succeeded by an accurate movement at high pressure. At low pressure the drawing die is first moved up to the workpiece. As soon as this has been done, the drawing process is carried out by means of a second larger piston. The pressure of the pressure medium always remains the same and increase of the force is obtained by using a larger piston face. The exertion of pressure on the larger and smaller piston faces always takes place in the direction of the supply (English Patent Specifications 845,l50 and 877,105).

The known devices suffer from the drawback of having to be constructed so as to be comparatively wide because the piston has a larger diameter so as to obtain the larger force. As a result of this, the dies in the known devices cannot be placed so as to be sufficiently close together.

It is the object of the invention to provide a device, in particular for drawing sheet metal, which has a diameter which is as small as possible.

In a device of the type mentioned in the preamble this object is achieved in that, according to the invention, the face of the pressure piston influenced in the supply direction by the pressure medium comprises a pressure rod which is connected to the piston and on which a further piston is axially movable which has a shell which encloses the pressure rodin a sealing manner, the shell guiding the pressure rod at a distance above the piston in a sleeve which is closed at its end and has a smaller inside diameter than the cylinder, the space in the sleeve being filled with a hydraulic liquid.

The largest diameter of the device is determined by the cylinder for the lower die pressure. The sleeve for the higher die pressure has a smaller outer diameter. This is achieved in that a pressure intensification is obtained in the space in the sleeve which is filled with hydraulic liquid by means of the shell which is movable on the pressure rod. The pressure intensification is larger as the annular face of the end of the shell is smaller relative to the end of the pressure rod.

Therefore, according to an advantageous embodiment of the invention, the annular face of the end of the shell is smaller by a multiple than the end face of the pressure rod which is present opposite to the closed end of the sleeve.

In itself it is sufficient when the pressure medium, which may be, for example, compressed air, is guided immediately between the pressure piston and the further piston. According to an advantageous construction of the invention, however, a partition plate which is connected to the sleeve is provided between the pressure piston and the further piston and through which the pressure rod is guided. In this manner there exists a certain separation between the pressure spaces for the pressure piston and the further piston, in which the pressure spaces have a fixed counter surface.

The invention will be described in greater detail with reference to an embodiment shown in the drawing.

A cylinder 1 of the device according to the invention is secured in a frame. The connection may be carried out, for example, to a plate 3, by means of the screws 5. -A piston 7 is axially movable in the cylinder 1. A drawing die 9 is secured to the piston 7 and projects through the plate 3. Via a duct 11, pressure medium, for example compressed air, is introduced into a pressure space 13 of the cylinder I. Said compressed air influences the piston face 15 and ensures that the piston 15 moves the drawing die up to a workpiece.

Projecting from the face 15, a pressure rod 17 is secured to the piston 7 and lies in the elongation of the drawing die 9. A partition plate 19 is provided in-the cylinder 1 and provides an upper abutment for the piston 7 and through which the pressure rod 17 projects.

The pressure rod 17 continues in a sleeve 21 having a smaller diameter. The sleeve 21 is closed at its upper end 23. The pressure rod 17 terminates near the upper end of the cylinder 21 and is freely movable relative to said end. A shell 25 is axially movable on the pressure rod 17. At its lower end, the shell is connected to a further piston 29 via a flange 27.

The pressure rod 17 is guided in the sleeve 21 by the upper end 31 of the shell 25. So the shell 25 is present between the inner wall 33 of the sleeve 21 and the surface 35 of the pressure rod which it encloses in a sealing manner. The cavity 37 between the pressure rod 17, the inner wall 33 of the sleeve 21 and the annular surface 39 of the end 31 of the shell is filled with a hydraulic liquid.

The operation of the device according to the invention is as follows:

First, a workpiece to be machined is placed below the presure die 9 which is brought upwards in the starting position in which a spacing disc 41 engages the partition plate 19. Compressed air is then admitted to the pressure spaces 13 and 43 via the duct 11. The compressed air acts in the pressure spaces 13 and 43 on the faces 15 and 48 of the pistons 7 and 29. As a result of this, the pistons 7 and 29 move downwards and upwards, respectively, and the drawing die 9 is placed on the workpiece. An intensified pressure is then built up in the pressure spaces 13 and 43 and the annular surface 39 of the shell 25 acts on the pressure liquid. Said pressure liquid influences the upper end face 45 of the pressure rod. Because the annular surface 39 is smaller by a multiple than the face 45 of the pressure rod, a hydraulic intensification is obtained which corresponds to the ratio of the size of the annular surfaces 39 and 45. When, for example, the upper end face A45 of the pressure rod is three times larger than the annular surface a 39 of the shell 25, the force acting on the upper end face 47 of the sleeve 21 is equal to 4.p.A39 and the pressure on the upper end face of the pressure rod A45 is equal to 3.p.A39. Herein p is the pressure with which the shell is forced upwards by the air pressure in the pressure space 43. The overall force F on the drawing die 9 is 3.p.A39 the pressure on the piston face 15.

When the further piston 29 moves only the shell 25 upwards, a hydraulic intensification of the laterally applied air pressure takes place. The pressure between the upper end face 45 of the pressure rod and the upper annular surface 39 gradually increases with the shell slowly sliding upwards until the force exerted on the workpiece to be drawn by the piston 7 via the drawing die and which is intensified by the force acting on the end face 45 of the pressure rod is sufficient to press the drawing die 1 in the workpiece. The alternation of the pressure build-up and movement of drawing die occurs so rapidly that the drawing process runs off smoothly.

The device according to the invention cannot only be used in drawing workpieces, such as sheet metal. It may advantageously be used also when a hydraulic supporting device (buffer, shock-absorber) having a small diameter is necessary.

Instead of compressed air, a hydraulic liquid for operating the device according to the invention may also be used without further measures.

What is claimed is:

1. Apparatus operable with a source of compressed fluid, for drawing sheet metal, comprising a housing defining therein a tubular bore having an upper part with a closed end and a lower part axially spaced therefrom, a first piston reciprocally movable in said lower part of the bore downward for said drawing operation and also upward, said piston having an exposed upper axial surface, means for communicating said compressed fluid to said exposed top surface for urging said piston downward, a rod extending axially upward from said piston into said upper part of the bore with an annular space defined between said rod and upper part, said rod having a top end and a pressure space is thereby defined between said closed end of the upper part of the bore and said top end of said rod, a second piston recipro- 'cally movable in said bore and comprising a base part with an exposed lower surface, and a sleeve part extending upward from said base and into said annular space, a hydraulic fluid in said annular space, means for communicating said compressed fluid to said exposed lower surface for urging said second piston upward, whereby said sleevemoves further into said annular space and urges said hydraulic fluid into said pressure space and against said top end of the piston rod, and thereby urges said rod and first piston downward, the axial area of said sleeve acting on fluid in said annular space being less than the area on said top end of the rod that isacted on by said fluid.

2. Apparatus according to claim 1 wherein said exposed lower surface of the second piston, and said exposed upper surface of the first piston, and portions of said bore define a single, continuous variable-volume compression space.

3. Apparatus according to claim 1 wherein said rod extends axially through the center of the second piston and said sleeve.

4. Apparatus according to claim 1 wherein said first and second pistons have substantially the same diameter, and said rods top end has a substantially smaller diameter than that of the pistons.

5. Apparatus according to claim 1 wherein said compressed fluid is gas.

6. Apparatus operable with a source of compressed gas, comprising a housing defining therein a tubular bore having a lower part of first diameter and axially spaced therefrom an upper part of smaller diameter with a closed end, first and second pistons in said lower I part with an intermediate space between them, means for communicating said compressed gas to said intermediate space for urging the first piston downward and the second piston upward, a rod thatextends from said first piston upward into said upper part of the housing with an annular space definedtherebetween, the rod having an end adjacent said closed end of said upper part of the bore with a compression space defined befluid in the annular space which acts in said compression space upon the end of said rod and urges same downward as a-supplemental force to said gas pressure which urges said first piston downward.

flag I UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3808872 Dated May 7, 1974 Inventor (x) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE TITLE PAGE:

The Assignee should be --U.S. PHILIPS CORPORATION-- Signed and sealed this 4th day of February 1975.

(SEAL) .Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN I I Attesting Officer Commissioner of Patents 7w UNITED STATES PATENT OFFICE v I CERTIFICATE OF CORRECTION Patent No. 38088 72 Dated May 7; 1974 Inventorhc) JOHANN MARTIN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE TITLE PAGE:

Change the Foreign Application Priority Data number from 2.165252" to --P. 2165 252 .8--

Signed and sealed this 24th day of September 1974.

(SEAL) Attest: MCCOY GIBSON JR. 2 c. MARSHALL DANN Attesting Officer I Commissioner of Patents 

1. Apparatus operable with a source of compressed fluid, for drawing sheet metal, comprising a housing defining therein a tubular bore having an upper part with a closed end and a lower part axially spaced therefrom, a first piston reciprocally movable in said lower part of the bore downward for said drawing operation and also upward, said piston having an exposed upper axial surface, means for communicating said compressed fluid to said exposed top surface for urging said piston downward, a rod extending axially upward from said piston into said upper part of the bore with an annular space defined between said rod and upper part, said rod having a top end and a pressure space is thereby defined between said closed end of the upper part of the bore and said top end of said rod, a second piston reciprocally movable in said bore and comprising a base part with an exposed lower surface, and a sleeve part extending upward from said base and into said annular space, a hydraulic fluid in said annular space, means for communicating said compressed fluid to said exposed lower surface for urging said second piston upward, whereby said sleeve moves further into said annular space and urges said hydraulic fluid into said pressure space and against said top end of the piston rod, and thereby urges said rod and first piston downward, the axial area of said sleeve acting on fluid in said annular space being less than the area on said top end of the rod that is acted on by said fluid.
 2. Apparatus according to claim 1 wherein said exposed lower surface of the second piston, and said exposed upper surface of the first piston, and portions of said bore define a single, continuous variable-volume compression space.
 3. Apparatus according to claim 1 wherein said rod extends axially through the center of the second piston and said sleeve.
 4. Apparatus according to claim 1 wherein said first and second pistons have substantially the same diameter, and said rod''s top end has a substantially smaller diameter than that of the pistons.
 5. Apparatus according to claim 1 wherein said compressed fluid is gas.
 6. Apparatus operable with a source of compressed gas, comprising a housing defining therein a tubular bore having a lower part of first diameter and axially spaced therefrom an upper part of smaller diameter with a closed end, first and second pistons in said lower part with an intermediate space between them, means for communicating said compressed gas to said intermediate space for urging the first piston downward and the second piston upward, a rod that extends from said first piston upward into said upper part of the housing with an annular space defined therebetween, the rod having an end adjacent said closed end of said upper part of the bore with a compression space defined between said bore and rod ends, hydrauliC fluid in said annular and compression spaces, a cylindrical sleeve extending upward from said second cylinder, generally surrounding said rod, and extending into said annular space, whereby when said gas urges said first piston downward and said second piston upward, the sleeve carried by said second piston applies pressure to said fluid in the annular space which acts in said compression space upon the end of said rod and urges same downward as a supplemental force to said gas pressure which urges said first piston downward. 